Other instruments have used the combination of a comparator and a television type display to display time-varying signals. Some sophisticated devices convert analog signals to digital, store the digital signals in a memory then use them in a timed sequence to create images on a television type display.
Sophisticated displays have found application in fields of science, medicine and commerce. There are other fields where simple devices would be useful. On such field is test equipment used by service technicians when repairing television receivers and other electronic equipment.
For example, to align the tuned intermediate frequency amplifier circuits of a television receiver, the recommended equipment includes a oscilloscope, a sweep signal generator, a marker generator, a marker-adder. The recommended procedure calls for interconnections between these instruments and the television receiver being aligned. It also calls for phasing and synchronizing adjustments between these instruments and successive changes of connections between the test equipment and the receiver being aligned.
The invention described herein is designed to improve and simplify the alignment of television receivers and be useful in other fields where a simple display is adequate. In the prior patents the common characteristics are:
A. A TELEVISION TYPE RASTER DISPLAY INCLUDING A VIDEO AMPLIFIER AND A FRAME SYNCHRONIZATION CIRCUIT.
B. A FIRST TIME-VARYING SIGNAL WHICH IS TO HAVE ITS WAVEFORM DISPLAYED.
C. A COMPARATOR WHICH HAS THE FIRST TIME-VARYING SIGNAL APPLIED TO IT AND WHICH ALSO HAS A SECOND TIME-VARYING SIGNAL APPLIED TO IT, THE SECOND TIME-VARYING SIGNAL BEING SYNCHRONIZED WITH THE SCANLINES IN THE TELEVISION TYPE DISPLAY.
A major difference between the previous devices is in the type of comparator used.